The present invention relates to a defect review apparatus, such as a review SEM, which is used to review and analyze the details of a sample's defect that is detected as defect coordinates by a defect inspection apparatus. The present invention also relates to a method for reviewing and analyzing the details of a defect with a review SEM or other defect review apparatus.
For improvement of yield in semiconductor manufacturing, it is important that the cause of defect generation during a manufacturing process be immediately investigated. At semiconductor manufacturing sites, defects are currently analyzed with a defect inspection apparatus and a defect review apparatus. The defect inspection apparatus reviews wafers with optical means or electron beams and outputs detected defect coordinates. It is important that the defect inspection apparatus rapidly process a broad area. Therefore, the defect inspection apparatus reduces the amount of image data by maximizing the pixel size (that is, by lowering the resolution) of an image to be acquired. In most cases, a detected low-resolution image may indicate the presence of any existing defect, but does not precisely identify its type. Under such circumstances, the defect review apparatus is used to precisely identify the type of a defect detected by the defect inspection apparatus. The defect review apparatus uses an output generated by the defect inspection apparatus, picks up a high-resolution image of a wafer at defect coordinates, and outputs the picked-up image. As the defect size is now on the order of several tens of nanometers due to an increased degree of miniaturization, the semiconductor manufacturing process requires a resolution on the order of several nanometers in order to review the details of defects. As such being the case, a defect review apparatus based on a scanning electron microscope (hereinafter referred to as the review SEM) has been widely used in recent years. An automated defect review operation is called for in a semiconductor mass production line. As described in JP-A-2001-331784, the review SEM incorporates an ADR (automatic defect review) function, which automatically acquires an image at defect coordinates of a sample, and an ADC (automatic defect classification) function, which automatically classifies acquired images.
Conventional technologies incorporated into a defect review apparatus composed of a review SEM are also described in JP-A-2001-189358, JP-A-2000-67243, JP-A-2007-40910, and JP-A-2007-3212.
The technology described in JP-A-2001-189358 is such that the inspection result information cut out from a defect inspection apparatus includes the information about a comparison target in addition to the information about a defect. The microscope system (review SEM system) described in JP-A-2001-189358 detects a defect image and a comparison target image in accordance with the comparison target information and compares the images to locate the defect.
The technology described in JP-A-2000-67243 is such that an electron microscope is used to automatically detect singularities (e.g., refraining from moving to a reference point when no pattern or repetitive patterns are encountered) in accordance with defect/foreign matter coordinates and other inspection result information cut out from a defect inspection apparatus, and review or process the information about the detected singularities.
A defect review apparatus described in JP-A-2007-40910 uses a scanning electron microscope to acquire a low-magnification image showing a defect in a sample, which is detected by an inspection apparatus, synthesizes a reference image by making use of the recurrence period of a circuit pattern that is imaged on the basis of the acquired low-magnification defect image showing the defect, detects the defect by comparing the synthesized reference image and the acquired low-magnification defect image showing the defect, and picks up a high-magnification image of the detected defect.
An imaging recipe creation apparatus described in JP-A-2007-3212 creates an imaging recipe for reviewing a semiconductor pattern with a scanning electron microscope. This image recipe creation apparatus includes a database and an imaging recipe creator. The database receives the layout information about a semiconductor pattern (an image picked up with a scanning electron microscope, CAD data containing the design information about the semiconductor pattern, or a CAD image obtained by converting the CAD data containing the design information about the semiconductor pattern into image data) in a low-magnification visual field and stores the input information. The imaging recipe creator automatically creates the imaging recipe by following an automatic creation algorithm containing a selection rule for selecting an imaging point optimized by means of teaching based on the semiconductor pattern layout information stored in the database.
In recent years, the number of defects to be reviewed per wafer has increased due to an increase in the diameters of semiconductor wafers. In addition, the defect review apparatus, such as a review SEM, exhibits a lower throughput than the defect inspection apparatus. Consequently, the speed of ADR needs to be increased.
In ADR, a considerable amount of time is generally spent on moving a stage between an initial position and a target position and on picking up a reference image and a defect image. Therefore, the speed of ADR can be effectively increased by shortening the time required for stage movement and eliminating some imaging procedures. However, such an increase in the speed of ADR is not sufficiently studied in any of the above-mentioned patent documents.
To consistently detect defects in a sample (semiconductor wafer) at a high throughput with a review SEM or other defect review apparatus, a user of the apparatus has to properly select and set up various defect detection methods in accordance with various characteristics of the sample to be placed on the apparatus. However, the proper selection and setup of various defect detection methods according to the various characteristics of the sample are not sufficiently studied in any of the above-mentioned patent documents.